What is the difference between rotor and stator?
Stator vs. RotorWhen working with electrical machines, you’ll come across two essential components — the stator and the rotor. While both are crucial to the machine’s operation, they have distinct characteristics and serve different purposes. In this discussion, we’ll compare the stator and rotor, highlighting their unique traits and explaining how each contributes to the functioning of rotating electrical machines.
What is a Stator?
The stator is the static or stationary part of a rotating electrical machine. It remains immobile while the machine is in operation. Typically, the stator forms the outer frame and magnetic circuit of the machine, constructed from cast iron. Inside the stator, a laminated stator core with slots holds the stator windings. The primary functions of the stator are to generate a working magnetic field and provide mechanical protection to the internal components of the machine.
What is a Rotor?
In contrast to the stator, the rotor is the moving or rotating part of the electrical machine. It consists of a rotor core and rotor windings. The rotor core is comprised of thin laminations of sheet steel with slots on its outer periphery to accommodate the rotor windings. When a current flows through the rotor windings, the resulting magnetic field interacts with the stator magnetic field, generating an electromagnetic torque that causes the rotor to rotate. In the case of an electric generator, an external prime mover is employed to rotate the rotor, inducing an electromotive force (emf) in the stator winding.
Differences between Stator and Rotor
The following table outlines the key distinctions between the stator and rotor in a rotating electrical machine:
| Key | Stator | Rotor |
|---|---|---|
| Definition | The stationary or static part of the machine. | Moving or rotating part of the machine. |
| Movement | Does not move. | Rotates inside the machine. |
| Position | Generally located externally. | Usually positioned internally. |
| Major sub-parts | Stator frame, stator core, and stator winding. | Rotor shaft, rotor core, and rotor winding. |
| Insulation level | Requires heavy insulation. | Requires less insulation compared to the stator. |
| Nature of current | Carries alternating current (AC) or direct current (DC). | Always carries alternating current (AC). |
| Mechanical losses | Low mechanical losses as it remains stationary. | High mechanical losses as it is in motion. |
| Total losses | Lower total losses, primarily electrical losses. | Higher total losses, including mechanical and electrical. |
| Physical size | Larger size, providing housing for the entire assembly. | Smaller size compared to the stator. |
| Cooling | Efficient cooling system, easy to maintain, and cost-effective. | Complex cooling system, less efficient, and relatively expensive. |
| Significance | Acts as an intermediary between electrical and mechanical systems. | Serves as an electrical-to-mechanical energy converter. |
Conclusion The stator and rotor are critical components that contribute to the functioning of rotating electrical machines. While the stator remains stationary, housing the machine’s core and windings, the rotor rotates and converts electrical energy into mechanical energy. Understanding the differences between these components is important in comprehending the distinct roles they play in the operation of electrical machines. The stator acts as a bridge between the electrical and mechanical systems, while the rotor serves as the key component responsible for the conversion of electrical energy to mechanical motion.